A “power supply” is a circuit that supplies electric energy to an electrical or electronic device. Power supplies used in modern electronic devices include, for example, batteries, Direct Current (DC) supplies, Alternating Current (AC) supplies, etc.
In some cases, a power supply may convert electric energy from one form to another. For instance, a “DC-to-DC converter” is a type of power supply capable of transforming a given DC voltage level into another (i.e., higher or lower) DC voltage level. Such a converter may be used, for example, in an electronic device that contains two or more circuits, each circuit having its own voltage requirement(s) that may be different from the voltage provided by the device's power supply.
An example of a DC-to-DC converter is the “charge pump.” A charge pump may use capacitor(s) and switching circuit(s) to create a higher or lower voltage source from the same power supply. To generate a high voltage from a lower-voltage power supply, for example, a switching circuit may be configured such that a capacitor is connected across the power supply, thus allowing the voltage across the capacitor (Vc) to approximate the power supply's voltage (Vdd). Then, the switching circuit may assume another configuration such that the capacitor is connected in series with the power supply. As a result, the output of the charge pump is equal to the sum of the power supply's voltage and the capacitor's voltage (i.e., Vout=Vdd+Vc≅2 Vdd), thus effectively doubling the supply voltage to the load (ignoring leakage and other effects).